Increasing the open loop gain of an amplifier is a method that may be used to improve the performance of a linear regulator comprising the amplifier. One method for increasing or boosting the open loop gain is the use of cascade stages. However, such methods may introduce drawbacks as they increase the design complexity and as they may lead to stability issues. Hence, there is a great interest at gain boosting methods which do not add hardware overhead.
A further method for boosting the open loop gain is to use a positive feedback. However, using a positive feedback may force the amplifier to an unstable state during operation.
Power management blocks such as linear drop-out regulators (LDO) may also take advantage of amplifiers with gain boosters. The gain boosting in LDOs may improve the power supply rejection ratio (PSR) and load regulation values. However, gain boosting methods which use positive feedback are typically limited to a positive feedback gain γ<½. Keeping the positive feedback gain γ<½ typically ensures stability, however, such values limit the possibilities for gain boosting. In other words, amplifiers in LDOs may incorporate positive feedback for gain boosting but only with a limited gain.